把代数式ax²-4ax+4a分解因式，下列结果中正确的是（　　）

完形填空

    Things can become very dangerous in a fire. 1 will you do if you cannot get out of the room?

    If you cannot get out of the room, close the door and put blankets (毛毯) at the 2 of the door. They can 3 the smoke from coming in.

    And 4 119 for help. Then open the window and 5 for help. Wave (摇摆) a piece of cloth from the window. Let people know that you are still inside the room.

    Don't stay under the bed or in the wardrobe. When the firefighters come in, they will have to 6 you. So stay by the window.

    If your clothes 7 fire, remember the words: stop, drop and roll.

    Stop running. Moving around will make the fire even 8. Drop and lie down on the floor. Roll around, from one side to 9 to stop the fire.

    If your friend's clothes are on fire, don't let him or her 10. Shout, "Stop, drop and roll!" When he or she is rolling on the floor, you can use a blanket or other heavy cloth to help to put out the fire on his or her clothes.

下列各数：$\frac{23}{7}$、3π、$\sqrt{12}$、$\sqrt[3]{27}$、cos30°中，无理数共有____ 个．

选修4-5：不等式选讲

已知函数f（x）=|x﹣ $\frac{1}{2}$ |+|x+ $\frac{1}{2}$ |，M为不等式f（x）＜2的解集．